DE102015010455A1 - heat exchangers - Google Patents

Abstract

The invention relates to a heat exchanger having a first cylinder tube (2) and a coaxial in the first cylinder tube (2) extending threaded spindle (3), wherein the inner surface of the first cylinder tube (2) has guide grooves (22) and wherein on the threaded spindle (3) Cleaning element (12) is mounted such that the cleaning element (12) by rotation of the threaded spindle (3) in the axial direction along the guide grooves (22) is displaced.

Description

The present invention relates to a heat exchanger, in particular for natural gas as a working medium for the purpose of drying and cleaning the natural gas.

State of the art

Heat exchangers for heating or for cooling a working medium are widely known from the prior art. Without restricting generality, the working medium natural gas will be considered in more detail below. Natural gas from soil reservoirs often has a particularly high percentage of unwanted accompanying substances and particularly high proportions of water. It is desirable to remove the impurities as well as the water content from the natural gas before it is used for further purposes. One possibility for this is the cooling of the natural gas in one or more steps to suitable low temperatures. In particular, in this case, a liquefaction of the natural gas may be appropriate.

During the cooling of natural gas, sediments on the heat transfer surfaces usually occur due to the aforementioned accompanying substances in the heat exchanger, the time course of such deposits depending on the operating conditions and the respective natural gas composition. The heat transfer surfaces must therefore be cleaned at certain intervals. For the reasons mentioned, however, it is difficult to specify generally valid cleaning intervals for the relevant heat exchangers.

Known gas dryer systems, for example, work with beds of porous materials such as silica gel. Another method used to dehumidify the working gas triethylene glycol, the process must usually be kept in several stages in order to achieve the desired purity can. Moist working gases are the cause of hydrate formation and corrosion. The gas transport networks therefore have limits on the water content.

Compressor stations and downstream elements, such as piping, valves, etc., are basically designed for operation with dry working gas, which is why in addition to impurities and water should be removed from the working medium. The process of gas drying may include, for example, mechanical steps (mechanical separation of free water) and thermodynamic steps (deposition by pressure reduction), and finally the step of absorption, for example, by highly hygroscopic substances such as said triethylene glycol. The triethylene glycol, can be sprayed into the gas stream and absorbs the remaining water.

Condensing and freezing impurities such as water, CO2 and hydrocarbon compounds separate on the heat transfer surfaces and thus reduce the heat transfer. Even at operating temperatures above the freezing point of water, formation of methane hydrate occurs at the heat transfer surfaces.

The porous beds in dryer systems according to the prior art inherently require a very large volume. Furthermore, the beds absorb only the liquid content, especially the water content, from the working gas. When regeneration of the bed, which takes place, for example, by flowing through with a dry unsaturated inert gas and / or heating and / or setting of the bed, a large proportion of working gas is discharged unused. When replacing the bed is in known dryers according to the prior art, an opening of the container necessary to replace the bed completely. This is costly and labor intensive and leads to an interruption of the production cycle.

The processes mentioned for drying and purifying gases as a working medium prove to be expensive. It is desirable to reduce the number of process steps without incurring the above-mentioned disadvantages.

Summary of the invention

The invention proposes a heat exchanger with a first cylinder tube and a coaxially extending in the first cylinder tube threaded spindle, wherein the inner surface of the first cylinder tube has guide grooves and wherein on the threaded spindle, a cleaning element is mounted such that the cleaning element by rotation of the threaded spindle in the axial direction along the Guide grooves is moved. This cleaning element is used to clean deposits on the heat transfer surfaces between the inner surface of the first cylinder tube and the threaded spindle. This cleaning element is mounted either directly in the form of a driver on the threaded spindle or attached to such a driver, which in turn is mounted directly on the threaded spindle. A working medium, which flows for heat exchange in a space between the first cylinder tube and the threaded spindle is - as explained above - especially on cooling deposits on the heat transfer surfaces. For natural gas as a working medium, these deposits consist in particular of impurities and water. The mentioned Deposits can be absorbed by the cleaning element and / or transported away or taken away. For cleaning, therefore, the threaded spindle is actuated, whereby the cleaning element is displaced in the axial direction within the first cylinder tube, whereby it can remove deposits from the heat-transferring surfaces. Such deposits occur in particular on the threaded spindle and on the axially extending guide grooves of the heat exchanger. The cleaning element cleans these surfaces. For the cleaning element, preferably steels, in particular tempered steels and alloys of non-ferrous metals, furthermore cold-tenacious nickel alloys (such as Inconel) as well as cast materials can be used.

During normal operation of the heat exchanger, the cleaning element is in a rest position in which it has the lowest possible or no influence on the heat exchange between working fluid and coolant. Of course, instead of a coolant, the use of a heating medium is also possible if the working medium is to be heated. The cleaning takes place, for example, according to empirically determined periods or when an externally measured maximum permissible differential pressure is reached, which can be deduced from a reduction of the free flow cross section for the working medium due to deposits.

The heat exchanger with cleaning element according to the invention allows effective cleaning of the heat transfer surfaces, without having to be opened manually. The described cleaning process is easy to carry out. For this purpose, only the threaded spindle must be rotated to move the cleaning element in the axial direction. Further process steps are not required. It is particularly advantageous if the cleaning element entrains or removes existing deposits. In this way, a change and thus wear or aging of the cleaning element can be prevented.

Advantages and embodiments of the invention

The coolant used for heat exchange without restriction of generality flows around an outer surface of the first cylinder tube. For this purpose, it is advantageous if the heat exchanger has a second cylinder tube which is arranged coaxially with the first cylinder tube. In this context, it is also expedient if an inlet and an outlet opening for the coolant is present in order to enable or dispense coolant into and out of a gap between the second and first cylinder tubes. In the same way, it is expedient if an inlet and an outlet opening for a working medium is present in order to let the working medium into or out of a gap between the first cylinder tube and the threaded spindle.

It is advantageous if the cleaning element is designed as a substantially hollow cylindrical cleaning element, wherein the inner surface of the cleaning element has an internal thread corresponding to the thread of the threaded spindle and wherein the outer surface of the cleaning element has outer grooves corresponding to the guide grooves of the inner surface of the first cylinder tube. In this way, the cleaning element in a simple manner (without a separate driver) are mounted on the threaded spindle and clear as possible existing deposits on heat-transmitting inner surfaces in the space between the inner surface of the first cylinder tube and threaded spindle.

It is expedient if the cleaning element has recesses in the otherwise substantially cylindrically shaped circumference of the cleaning element, these recesses extending parallel to the axial direction. These recesses are arranged equidistantly in particular in the cleaning element in the circumferential direction. The recesses or "mills" create "teeth" or "claws" in the cleaning element, which in particular help to prevent seizure or blockage of the cleaning element during cleaning. From the threaded spindle dissolved deposits can get into said recesses or milled and fall from there in vertical operation of the heat exchanger at least in the cleaning phase down (in the direction of movement of the cleaning element). In this way, a blockage of the cleaning element can be effectively avoided by accumulating deposits.

Furthermore, it is expedient if the internal thread of the cleaning element has a diameter which increases in the axial direction. By this configuration it is achieved that the cleaning of the thread grooves is not as abrupt as for example in a cleaning element which rests in the axial direction over its entire extent on the thread grooves. As a result, a possible clamping of the cleaning element is avoided. In connection with the above-mentioned embodiment, in which the cleaning element has axial recesses, the individual "claws" or "teeth" produced thereby become more elastic and press better against the outer wall or to the thread grooves. Another advantage is the free space formed thereby, comparable to a chip channel of a machining process.

It is advantageous if the outer surface of the first cylinder tube in the axial direction having spirally extending helix. This helix is part of the outer surface of the first cylinder tube and is applied to this outer surface or produced by milling. In the interstices of this coil then the coolant can flow in a spiral in the axial direction. This first cylinder tube with this helix can therefore also be referred to as a cooling helix.

It is advantageous if a deposit storage for depleted by the cleaning element deposits / impurities with the gap between the threaded spindle and the inner surface of the first cylinder tube / cooling coil is in particular thermally decoupled connected. In this advantageous embodiment, the cleaning element transports contaminants into the deposit storage, which is thermally decoupled in particular from said heat-transferring surfaces, ie the gap between the threaded spindle and the inner surface of the first cylinder tube. This thermal decoupling allows a thermal treatment of the accompanying substances collected in the deposit accumulator or other deposits without influence on the further operation of the heat exchanger. For this purpose, a heating element is advantageously present in or on the heat exchanger and arranged such that accompanying substances / impurities present in the deposit storage can be heated. When the working medium cools down, the contaminants present in the working medium, such as impurities and water, condense out. The cleaning element can transport the condensed impurities into the deposition reservoir, which can then also be referred to as a condensate reservoir, for example. The collected condensate can then be heated by means of said heating element. The heated, melted condensate can be drained by opening a downstream valve via a condensate drain. In this way, at given times the deposit storage in turn can be freed from existing impurities.

It is useful to obtain knowledge of the position of the cleaning element during the cleaning process. For this purpose, a position measuring means is advantageously present and arranged such that the position of the cleaning element in the axial direction can be measured. Such a position measurement allows or makes it easier to reverse the direction of rotation of the threaded spindle at a certain predetermined position, so that the cleaning element moves back in the opposite direction. Also, the reaching of a predetermined rest position by means of the position indicator can be detected in a simple manner.

To drive the threaded spindle, it is advantageous to use a drive motor, wherein between the drive motor and the gap between the threaded spindle and the inner surface of the first cylinder tube, ie between the drive motor and the heat-conducting surfaces of the heat exchanger, a particle barrier is present. Such a particle barrier prevents the penetration of foreign substances into the space in which the working fluid flows to the heat exchanger, and conversely serves to protect the drive motor or its bearing from particles.

In summary, the following preferred structure of a heat exchanger according to the invention can be stated, wherein the individual features need not necessarily be realized in the combination specified here. The internal threaded spindle is surrounded by a first cylinder tube or the cooling coil. The latter is in turn surrounded by a second cylinder tube or an outer cylinder tube. The space between the threaded spindle and cooling coil forms the working space for the working medium, which is supplied via an inlet opening of this space and removed via an outlet opening of this space after heat exchange. It may be expedient to reverse the flow direction, wherein for this purpose the said inlet opening is used as the outlet opening and the said outlet opening as the inlet opening. In such a case, however, it is advantageous to provide on the side of said inlet opening a further outlet opening and on the side of said outlet opening a further inlet opening for the working medium on the heat exchanger. In this case, two opposite ports are each available for the inlet and for the outlet of the working medium, which are also referred to below as the "double-sided" inlet opening or as a "double-sided" outlet opening. A coolant is added to the gap between the cooling coil and the outer cylinder tube via a coolant inlet opening and flows through this intermediate space to a coolant outlet opening in order to leave this intermediate space again. For the coolant inlet and outlet opening applies in a similar manner to that for the inlet and outlet opening for the working medium, that is, it is advantageous to provide a two-sided coolant inlet and outlet. It makes sense if the flow of the coolant takes place in countercurrent to the flow of the working medium. It may also be useful if the flow of the coolant takes place in cocurrent to the flow of the working medium.

On one side of the heat exchanger is a drive motor which rotates the threaded spindle. The threaded spindle is mounted in a warehouse. At this camp is a position measuring means, based on the number of Revolutions of the drive motor with a known pitch of the thread of the threaded spindle can provide information on the position of the moving of the threaded spindle cleaning element. The cleaning element, which can also be referred to as a scraper, is in its rest position preferably on the same side as the drive motor and is separated from it by a particle barrier. Such a particle barrier may for example be made of PTFE and is then so soft even at low temperatures that particles can accumulate therein. The radial distance to the shaft is as small as possible, ideally a few tenths of a millimeter, preferably less than 0.4 mm, more preferably less than 0.3 mm, more preferably approximately equal to 0.2 mm.

On the other side of the heat exchanger is located at the end of the working space through which the working fluid flows, a deposit storage or a condensate reservoir, which is thermally decoupled in particular from this working space. This is followed by a heating element that is thermally coupled to the condensate reservoir to heat it. The condensate reservoir is connected via a condensate drain with the environment of the heat exchanger to be able to empty the contents of the condensate reservoir. Also at this end of the heat exchanger is a plain bearing bush for the threaded spindle.

In the following, the operation of such an advantageous heat exchanger according to the invention is described in more detail: Depending on the flow direction flows through the respective working medium inlet wet, polluted working fluid in the space between the threaded spindle and cooling coil and flows in the direction of the opposite outlet opening. The working medium flows in the guide grooves of the inner surface of the cooling coil along the axis of rotation of the threaded spindle. The cooling coil is extracted by a coolant heat, said coolant flows preferably in countercurrent to the working fluid in the space formed between the cooling coil and outer cylinder tube. Due to this cooling, the temperature of the working medium falls off and impurities or impurities fall out according to their liquefaction or solidification temperatures at the heat transfer surfaces. These impurities reduce the heat transfer capacity between the working medium and the cooling coil.

For the purpose of cleaning the heat transfer surfaces, the threaded spindle is rotated by the drive motor. The housing of the drive motor is preferably connected to the intermediate space through which the working fluid flows, and thus loaded with the operating pressure. The thread of the threaded spindle is preferably designed as a right-hand thread with trapezoidal profile, which in principle also left-hand thread and other flank shapes can be conceivable and advantageous. Please also refer to the below. The cleaning element or the reamer engages on the one hand in the thread of the threaded spindle and on the other hand in the guide or profile grooves of the cooling coil, whereby the cleaning element is placed in a translational movement.

Due to the defined thread pitch of the threaded spindle, the position of the cleaning element can be detected with the aid of the number of revolutions of the drive motor measured by the position means. The cleaning element slides up to the thermally decoupled condensate reservoir or deposit storage at the end of the working space. The cleaning element thus pushes the existing entrained deposits in the condensate reservoir. Once the appropriate position is reached, the direction of rotation of the drive motor is reversed and the cleaning element moves back to its rest position adjacent to the particle barrier. The collected condensate can be heated by the heating element and, depending on the physical state, caused to melt or evaporate and then be discharged by opening a downstream valve through the preferably two-sided condensate drain.

It is particularly advantageous to combine a plurality of series-connected heat exchanger to a heat exchanger system. Such a staged design can "freeze" contaminants as the individual stages are operated at lower temperatures.

As an alternative to the mentioned threaded spindle with trapezoidal profile, a threaded spindle with a cross thread can be advantageously used. Such threaded spindles are known per se and are referred to as cross-threaded spindles. Threaded spindles with trapezoidal profiles can always represent only one associated direction of movement according to their direction of rotation, which consequently also reverses when the direction of rotation is reversed. The reversal of the direction of rotation requires a switching element in the electrical supply of the drive motor or a change gear. In order to avoid overshooting defined end positions on threaded elements such as the cleaning element, they are often equipped with a position stop. Alternatively, the position of the sliding member is detected with a position detecting means.

The use of cross thread spindles overcomes these disadvantages. A cross thread is like that constructed that on a spindle both a left and a right-hand thread preferably each same pitch is shown, which has a reversal point in its respective end positions in which at least one sliding in the thread groove sliding block is transferred from a first direction of movement in a second direction of movement. The direction of rotation of the shaft of the threaded spindle thus always remains the same. Thus eliminates the need for the above-described position measuring means for the position of the cleaning element when using a cross-threaded spindle. For this purpose, the upper Endlagenbestimmung, ie the determination of the rest position of the cleaning element via an alternative method must be done. For this purpose, for example, a torque measurement is possible, registered the significant changes in torque in the two end positions of the cleaning element. Additionally or alternatively, the end positions or at least the upper end position of the rest position by means of initiators, so limit switch, can be determined.

In a simplified embodiment, the heat exchanger according to the invention consequently has a cross-threaded spindle with at least one sliding block, which slides in the threads and a clearing or cleaning element connected to the sliding block, for example via a bolt.

The advantages of using the cross-threaded spindle lie in an automatic reversal of the direction of movement, without changing the direction of rotation of the shaft, so that braking and restarting the electric motor is obsolete, which in turn results in a more energy-efficient process. Furthermore, as already stated, no electrical device for reversing the direction of rotation must be provided, or a corresponding program part in the control is dispensed with. Overall, the cleaning process of the heat exchanger is shortened by the omitted direction reversal. The end position of the cleaning element are automatically defined by the reverse grinding of the cross thread and can therefore not be run over. Finally, the position measuring means described above can be omitted.

The invention further relates to a use of the heat exchanger according to the invention for the liquefaction of a gas. In this case, a second cylinder tube is arranged coaxially with the first cylinder tube of the heat exchanger, wherein a coolant flows between the first and second cylinder tubes. Furthermore flows between the first cylinder tube and threaded spindle, a working medium containing the gas to be liquefied. In the example of natural gas described above, the gas to be liquefied may be, for example, nitrogen. The cooling medium flows at a lower temperature than the working medium, wherein the pressure and the temperature of the cooling medium and the pressure of the working medium are adjusted such that the heat to be liquefied by the heat exchange with the cooling medium in the working fluid. In the above-mentioned example of natural gas, for example, liquefied nitrogen can be used at a pressure of 1 bar and a temperature of -196 ° C. as the cooling medium. The working medium (natural gas) is introduced, in particular after appropriate precooling by upstream heat exchanger with a pressure of for example 10 bar. By heat exchange with the cooling medium, the nitrogen contained in the natural gas can be cooled to a temperature of -170 ° C and below, so that it liquefies at a pressure of 10 bar.

Said method can be used analogously to the liquefaction of helium, oxygen and / or hydrogen as one or more constituents in a working medium. Concrete examples of the liquefaction of helium, hydrogen and oxygen are given below:

Liquefaction of various gases, for example for the purpose of separation from gas mixtures

Liquefaction of O ₂ :

• Cooling medium preferably liquid nitrogen between 1 and 15 bar;
• Temperature range of the cooling medium -163 ° C @ 15 bar to -196 ° C @ 1 bar;
• Pressure of the O ₂ to be liquefied 1 bar-50 bar;
• first condensing temperature @ 1 bar -183 ° C;
• second condensing temperature @ 50 bar -119 ° C;
• The pressure of the cooling medium is chosen in each case so that the temperature of the cooling medium is always lower than that of the working medium.

Liquefaction of H ₂ :

• Cooling medium preferably liquid helium between 1 and 2.2 bar;
• Temperature range of the cooling medium -267 ° C @ 2.2 bar to -268 ° C @ 1 bar;
• The pressure of the cooling medium is chosen in each case so that the temperature of the cooling medium is always lower than that of the working medium.

• Alternative cooling medium Liquid hydrogen between 1 and 13 bar;
• Temperature range of the cooling medium -240 ° C @ 13 bar to -253 ° C @ 1 bar. In the special case that as cooling medium the same medium as the medium to be liquefied is used, the pressure in the cooling medium must be lower than the pressure of the working medium, so that the coolant temperature is lower due to the lower equilibrium point.

• Pressure of the liquefied H ₂ 1 bar-13 bar;
• first condensing temperature @ 1 bar -253 ° C;
• second condensing temperature @ 13 bar -240 ° C;

Liquefaction of He:

• Cooling medium preferably liquid helium between 1 and 2.2 bar;
• Temperature range of the cooling medium -267 ° C @ 2.2 bar to -268 ° C @ 1 bar;
• In the specific case that the same medium as the medium to be liquefied is used as the cooling medium, the pressure in the cooling medium must be lower than the pressure of the working medium, so that the coolant temperature is lower due to the lower equilibrium point.

• Pressure of the He liquefied 1 bar-2.2 bar;
• first condensing temperature @ 1 bar -268 ° C;
• second condensing temperature @ 2,2 bar -267 ° C;

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below with reference to the drawing.

Brief description of the figures

1 shows a schematic longitudinal section of an advantageous embodiment of a heat exchanger according to the invention,

2 shows a cooling coil as the first cylinder tube of in 1 illustrated heat exchanger,

3 shows a cleaning element, as in the heat exchanger according to 1 is inserted, and

4 schematically shows the section of a threaded spindle with a cross thread.

Detailed description of the figures

1 shows schematically a longitudinal section through an embodiment of a heat exchanger 13 as it can be used in particular for cooling natural gas. In this simple embodiment, the heat exchanger 13 an outer cylinder tube 1 on, that is a cooling coil 2 surrounds. This cooling coil 2 is in turn designed as a cylindrical tube and has at least one, preferably spiral channel 23 on its outer surface, which serves to guide a coolant. As in 2 represented, this channel becomes 23 through a suitable helix 21 on the outer surface of the cooling coil 2 generated. The inner surface of the hollow cylindrical cooling coil has guide or profile grooves 22 on. This at least one guide groove 22 serves to guide a cleaning element or scraper 12 ,

Inside the cooling coil 2 is coaxial with this one threaded spindle 3 , The threaded spindle 3 is powered by a drive motor 4 driven and is stored in a storage location, preferably as axial / radial mixed storage 5 is executed. At the other end of the threaded spindle 3 this is in a radial bearing, preferably as a plain bearing bush 8th is executed, stored. At this end of the heat exchanger 13 is also a thermally decoupled condensate reservoir 7 and a heating element 9 for heating condensate in the condensate reservoir 7 available.

At the other end of the heat exchanger 13 separates a particle barrier 11 the drive motor 4 from the working space for the working medium. The particle barrier 11 also serves to protect the drive motor 4 and the camp 5 against coarse particles, but does not act as a gas seal.

In the embodiment shown here according to 1 are several outer cylinder tubes 1 by a clamping device 10 connected. The clamping device 10 is constructed so that two coupling rings with an internal thread on the outer cylinder tube 1 , which in turn is provided with an external thread, are screwed on. The coupling rings are tightened by screws and the individual segments are pressed together and sealed by a seal. Also, several such outer cylindrical tubes can be understood and referred to as an "outer cylinder tube".

A cleaning element or scraper 12 is next to the particle barrier 11 arranged in its rest position. When commissioning the drive motor 4 becomes the threaded spindle 3 rotated so that the reamer 12 on the threaded spindle along the guide or profile grooves 22 the cooling coil 2 is moved in the axial direction. In the present An example will be a threaded spindle 3 used for example with trapezoidal profile. A reversal of the direction of movement of the reamer 12 sets a reversal of the direction of rotation of the threaded spindle 3 ahead. Another embodiment of the threaded spindle 3 is related below 4 explained.

In operation of the heat exchanger 13 is via a working medium inlet opening 14 For example, humid, polluted working fluid in the space between the threaded spindle 3 and between cooling coil 2 guided and flows in the axial direction to the working medium outlet opening 15 at the other end of the heat exchanger 13 , The working fluid flows in the profile grooves 22 on the inner surface of the hollow cylindrical cooling coil 2 (see. 2 ) along the axis of rotation of the threaded spindle 3 , Via a coolant inlet opening 16 is the space between cooling coil 2 and outer cylinder tube 1 Coolant supplied to the other end of the heat exchanger 13 flows and this through the coolant outlet 17 leaves. The coolant flows in the between outer cylinder tube 1 and cooling coil 2 formed channel 23 spiral in the axial direction. The coolant removes the cooling coil 2 Heat, which in turn removes heat from the working medium.

In a special application, natural gas is tempered from a subterranean cavern to a temperature of approx. 20 ° C with a pressure of 4 to a maximum of 220 bar. In a first heat exchanger, the working medium is cooled to preferably 1 ° C. In a second heat exchanger, which is connected in series with the first heat exchanger, the working medium is cooled to preferably -40 ° C to -60 ° C. In a third stage, the working medium is cooled to preferably -80 ° C to -150 ° C and in a final stage, the working fluid is liquefied via a turn connected in series heat exchanger. The temperature of the natural gas is lowered down to -196 ° C, which leads to supercooling of the natural gas. The first stage is a major part of the water content, the next stages mainly the higher hydrocarbons, CO ₂ and other impurities. By in the respective stages of the heat exchanger 13 existing scrapers 12 Condensed components can be cleaned from the heat-transferring surfaces.

The first two heat exchanger stages are cooled by chillers in this specific connection case, the other two by liquid nitrogen, cryogenic liquid CNG or by cryogenic gaseous nitrogen. The maximum operating pressure of the heat exchanger is 300 bar, the permissible operating temperatures are 100 ° C to -200 ° C.

Due to the different pressure ratios between the cooling medium, for example nitrogen at a maximum of 10 bar, and the working medium, here CNG with impurities including nitrogen from 4 to 220 bar, nitrogen as a companion at high pressure (eg. At 10 bar) by liquid nitrogen at low pressure (for example, at 1 bar), caused by the different pressure-dependent phase transitions to liquefy and deposited. The proposed here heat exchanger 13 can thus also be used for the liquefaction of nitrogen.

For the purpose of cleaning the heat transfer surfaces, for example of water or ice in the first stage and higher hydrocarbons, CO ₂ and other accompanying substances in the second and further stage, the threaded spindle is 3 a step by the drive motor 4 set in rotation. The reamer 12 , on the one hand in the thread of the threaded spindle 3 and on the other hand in the profile grooves 22 the cooling coil 2 engages, is thereby translated into a translational motion. On his way towards the condensate reservoir 7 takes the reamer 12 the said condensed accompanying substances with. These are on reaching the condensate reservoir 7 pushed into the same. The position measuring means 6 can due to the defined thread pitch of the threaded spindle 3 from the number of measured revolutions of the drive motor 4 the position of the reamer 12 determine. Once the position of the condensate reservoir 7 is reached, the direction of rotation of the drive motor 4 vice versa, so the reamer 12 wanders back to its resting position. It is expedient if the rest position the upper end position and the position of the condensate reservoir 7 the lower end position of the scraper 12 represents at a vertical position of the heat exchanger.

The collected condensate is transferred via the heating element 9 heated and thus melted. By opening a downstream valve, the accompanying substances can be separated by a condensate drain 18 be drained.

Cleaning the heat exchanging surfaces of the heat exchanger 13 takes place, for example, after empirically determined period lengths or when an externally measured maximum permissible differential pressure is reached, which indicates a reduction of the free flow cross section in the working space due to deposited impurities. The cleaning achieves the highest possible and constant heat transfer value. Compared to the prior art systems, the heat exchanger is claimed 13 due to the effectively used heat transfer surfaces a smaller volume.

The segmental structure of the heat exchanger 13 allows a modular design. The heat transfer performance is thus variable via the enlargement or reduction of the heat transfer surfaces.

By the use of said position detection means 6 always the actual position of the reamer 12 supervised. Any seizure can be detected early by measuring the slip.

It should be noted that the heat exchanger described here 13 Not only for natural gas liquefaction, but for a variety of industrial applications with appropriate working media can be adapted and used. The reamer 12 can be adapted as a less complex replacement part to the needs of the respective application areas and quickly replaced in the event of damage.

3 shows a reamer 12 or a cleaning element 12 as it is in the heat exchanger 13 can be used. Shown are the outer grooves 122 the reamer 12 that the guide grooves 22 the cooling coil 2 correspond. The internal thread 121 the reamer 12 corresponds to the thread of the threaded spindle 3 , The reamer 12 has recesses or milling 123 on. By the latter contains the reamer 12 "Teeth" or "claws", which prevent accumulate deposits in the thread and to block the reamer 12 to lead. The deposits can namely through the recesses or milled 123 enter the intermediate space and in the vertical position of the heat exchanger downwards towards the condensate reservoir 7 fall. Furthermore, the inner diameter of the reamer, which increases in the direction of movement of the cleaning, serves 12 for easier insertion into the contaminated threaded spindle at the beginning of the cleaning process.

4 finally shows an alternative embodiment of a threaded spindle 3 ' in which it is a cross-threaded spindle 3 ' is. The shaft with cross thread is with 31 designated. The sliding block running in it with 32 , In this embodiment, the reamer 12 with the sliding block 32 connected and moves during rotation of the threaded spindle 3 ' in the axial direction.

Advantage is here, as already explained above, that sliding in the thread groove sliding block 32 upon rotation of the threaded spindle 3 ' is transferred in a single rotational direction from a first direction of movement in a second, opposite direction of movement, without the rotational direction of the shaft 31 to change.

Due to the superposition of the left and right-hand thread forms on the shaft 32 a typical deltoid-shaped pattern.

As also described above, the threaded spindle allows 3 ' an energetically more economical process, since the electric motor does not have to be braked and restarted. In addition, a position measurement of the reamer 12 and thus the in 1 shown position measuring means 6 omitted. The cleaning process of the heat exchanger 13 is shortened again by the omission of the direction reversal.

LIST OF REFERENCE NUMBERS

1

Outer cylinder tube, second cylinder tube

2

Cooling coil, first cylinder tube

3, 3 '

screw

4

drive motor

5

Axial / radial bearings

6

Position measuring means

7

Condensate reservoir, deposit storage

8th

plain bearing bush

9

heating element

10

clamping device

11

particle barrier

12

Scraper, cleaning element

13

heat exchangers

14

Working fluid inlet port

15

Working fluid outlet opening

16

Coolant inlet opening

17

Coolant outlet opening

18

drain

21

spiral

22

Guide groove, profile groove

23

channel

121

Internal thread of the cleaning element

122

outer groove

123

Recess, milling

31

Shaft of the threaded spindle 3 '

32

slide

Claims (20)

Heat exchanger with a first cylinder tube ( 2 ) and a coaxial in the first cylinder tube ( 2 ) extending threaded spindle ( 3 ), wherein the inner surface of the first cylinder tube ( 2 ) Guide grooves ( 22 ) and wherein on the threaded spindle ( 3 ) a cleaning element ( 12 ) is mounted such that the cleaning element ( 12 ) by rotation of the threaded spindle ( 3 ) in the axial direction along the guide grooves ( 22 ) is moved. Heat exchanger according to claim 1 with a second cylinder tube ( 1 ) coaxial with the first cylinder tube ( 2 ) is arranged. Heat exchanger according to claim 1 or 2, wherein the outer surface of the first cylinder tube ( 2 ) a spirally extending spiral in the axial direction ( 21 ) having. Heat exchanger according to one of the preceding claims, wherein the cleaning element ( 12 ) as a substantially hollow cylindrical shaped cleaning element ( 12 ), wherein the inner surface of the cleaning element ( 12 ) an internal thread ( 121 ) corresponding to the thread of the threaded spindle ( 3 ) and wherein the outer surface of the cleaning element ( 12 ) Outer grooves ( 122 ) corresponding to the guide grooves ( 22 ) of the inner surface of the first cylinder tube ( 2 ) having. Heat exchanger according to Claim 4, in which the cleaning element ( 12 ) Recesses ( 123 ) in the otherwise substantially cylindrically shaped circumference extending parallel to the axial direction. Heat exchanger according to claim 5, wherein the recesses ( 123 ) in the cleaning element ( 12 ) are arranged equidistantly in the circumferential direction. Heat exchanger according to one of claims 4 to 6, wherein the internal thread ( 121 ) of the cleaning element ( 12 ) has a diameter which increases in the axial direction. Heat exchanger according to one of the preceding claims, wherein an inlet and an outlet opening ( 16 . 17 ) is present for a coolant, in order to coolant into or from a space between the second cylinder tube ( 1 ) and first cylinder tube ( 2 ) on or off. Heat exchanger according to one of the preceding claims, wherein an inlet and an outlet opening ( 14 . 15 ) is provided for a working fluid to the working fluid in or out of a space between the first cylinder tube ( 2 ) and threaded spindle ( 3 ) on or off. Heat exchanger according to one of the preceding claims, wherein a deposit memory ( 7 ) for by means of the cleaning element ( 12 ) cleaned impurities with the space between threaded spindle ( 3 ) and inner surface of the first cylinder tube ( 2 ) is connected in particular thermally decoupled. Heat exchanger according to claim 10, wherein a heating element ( 9 ) and arranged such that in the deposit memory ( 7 ) existing impurities can be heated. Heat exchanger according to one of the preceding claims, in which a position-measuring means ( 6 ) and arranged such that the position of the cleaning element ( 12 ) can be measured in the axial direction. Heat exchanger according to one of the preceding claims, wherein for driving the threaded spindle ( 3 ) a drive motor ( 4 ), and wherein a particle barrier ( 11 ) between drive motor ( 4 ) and the space between threaded spindle ( 3 ) and inner surface of the first cylinder tube ( 2 ) is available. Heat exchanger according to one of the preceding claims, wherein the threaded spindle ( 3 ) has a trapezoidal profile as a thread profile. Heat exchanger according to one of claims 1 to 13, wherein the threaded spindle ( 3 ' ) as thread has a cross thread. Heat exchanger according to claim 15, in which in the thread groove of the cross thread of the threaded spindle ( 3 ' ) a sliding block ( 32 ) is slidably mounted with the cleaning element ( 12 ) connected is. Heat exchanger system with a plurality of series-connected heat exchangers according to one of claims 1 to 16. Use of a heat exchanger according to any one of claims 1-16 for the liquefaction of a gas, in which coaxial with the first cylinder tube ( 2 ) a second cylinder tube ( 1 ), wherein between the first and second cylinder tube, a coolant flows, wherein between the first cylinder tube ( 2 ) and threaded spindle ( 3 ) flows a working medium containing the gas to be liquefied, and wherein the cooling medium flows at a lower temperature than the working fluid, wherein the pressure and temperature of the cooling medium and the pressure of the working medium are adjusted such that to be liquefied by the heat exchange with the cooling medium Gas in the working medium liquefies. Use according to claim 18, wherein the same medium as the gas to be liquefied is used as the cooling medium, wherein the pressure of the cooling medium is chosen to be lower than that of the working medium. Use according to claim 18 or 19 for the liquefaction of nitrogen, helium, oxygen and / or hydrogen as one or more components in the working medium.

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